Japanese Patent Application Publication No. 2011-082220 (hereinafter referred to as Patent Literature 1) discloses a semiconductor device that has a cathode layer, a buffer layer, and a drift layer. The cathode layer has a high n-type impurity concentration, and is exposed on a back surface of a semiconductor substrate. The buffer layer has an n-type impurity concentration lower than that of the cathode layer, and is in contact with the cathode layer. The drift layer has an n-type impurity concentration lower than that of the buffer layer, and is in contact with the buffer layer.